Localized atrophy of the pontine base as a sequela of prolonged ischemia: Report of an autopsy case.

An 80-year-old man with a history of diabetes mellitus and hypertension died of a progressive neurological disorder characterized by truncal ataxia, extraocular movement disturbance, and muscular rigidity. Neuroradiological examination showed progressive atrophy restricted to the pontine base. Autopsy revealed localized atrophy of the pontine base, in which both neurons and nerve fibers were lost, especially in the central region. Medium-sized and small arteries in the parenchyma of the pontine base showed marked fibro-hyalinous thickening of the walls with luminal stenosis, but no distinct tissue defect as seen in lacunar infarct was observed. Perivascular lymphocytic infiltration was mostly absent, and reactive astrocytic proliferation was weak. The pontine tegmentum, midbrain, and medulla oblongata were well preserved. Localized atrophy of the pontine base is a rare pathological condition, and its pathogenesis in the present case can be best explained by a prolonged ischemic state (hypoperfusion) due to marked sclerotic changes of perforating arteries. It is unique that the lesions were restricted to the pontine base and the formation of lacunas was not observed. Localized metabolic derangement resembling that seen in central pontine myelinolysis might have also contributed to the pathogenesis of this peculiar localized atrophy.